This invention relates to a clamping device for formwork, which is a temporary mould in which concrete, other settable materials, rammed earth and the like can be placed. The invention will be described with reference to concrete formwork, but other uses of the formwork are envisaged.
The function of formwork is to hold fluid concrete into the desired shape, to support fresh concrete until it is strong enough to be self-supporting, and to support temporary loading such as runways and machinery used to place the concrete.
Formwork should be simple to erect and dismantle. Only the minimum number of fasteners should be used. The formwork must remain straight and rigid when concrete is poured and therefore adequate bracing is essential to prevent movement caused by vibrators, concrete pumps and other machinery. The formwork should be tight to prevent loss of xe2x80x9cfinesxe2x80x9d. Any leaks can produce honeycombing or ridges on the finished concrete. Formwork should also be constructed such that maximum re-use is possible.
Formwork panels are made of wood boards, steel sheets, hard boards or resin bonded plywood. In order to allow the formwork to be made portable, the boards or sheets are relatively thin and therefore must be supported.
Formwork junctions must be able to support quite large forces and stresses, and the formwork must not warp, bow, or leak. Angled formwork, that is where adjacent formwork panels meet at an angle, require special consideration, and to date, complicated and unwieldy support devices are used to clamp formwork panels together at an angle. These existing devices are complicated to use, and readily become unusable should minimum contamination occur. That is, should small amounts of wet cement fall on to existing devices, the devices either cease to function or must be cleaned prior to use.
It is an object of the invention to provide a clamping device to hold adjacent formwork panels, with the clamping device being simple, robust and easy to assemble and disassemble.
It is a further object of the invention to provide a clamping device for formwork panels which may overcome the abovementioned disadvantages or provide the public with a useful or commercial choice.
In one form, the invention resides in a clamping device to hold adjacent formwork panels, the clamping device having a backing plate against which edges of the adjacent formwork panels can be held, at least one rod extending from the backing plate, and a clamping member able to move along the rod between a clamping position where the member clamps the formwork panels against the backing plate, and a free position where the formwork panels can be removed.
The above arrangement is-simple and can be used to clamp formwork panels to form corners of 90xc2x0, 45xc2x0, or any other angle, and can also be used, if desired, to clamp adjacent panels in a straight line.
The backing plate is suitably elongate and is preferably sufficiently long to enable the entire edge of a formwork panel to be held. The backing plate should be made of rigid material which does not bend or bow during a concrete pour. Thus, the backing plate is normally made of steel.
To allow adjacent formwork panels to be held by the backing plate, the backing plate typically has two opposed flanges, each flange able to support an edge area of a formwork panel. The opposed flanges can be angled relative to each other to form a corner of a desired angle.
Extending from the backing plate is at least one said rod on which the clamping member can be supported. If the backing plate is of sufficient length, a number of rods can be provided, the rods being spaced apart and along the backing member, the rods extending from the same side of the backing plate.
To provide a good, strong, secure connection between the rod and the backing plate, the rod can be attached to a boss or protrubance which itself is attached to the backing plate.
The rod can be releasably attached to the backing plate. In one form, the rod can be releasably attached to a mount which is attached to the backing plate. In a simple form, one end of the rod is bent, or has an angled portion which is held by a collar fastened to the backing plate.
If the rod is attached to a protrubance, the protrubance may have sides against which edges of the formwork abut. This arrangement can minimise movement of the formwork panels, and can also serve to align the formwork panels and the clamping device.
The rod may be formed from steel and may be solid or hollow. In a simple embodiment, the rod can be threaded to accommodate the clamping member.
The clamping member may comprise a clamping plate. The clamping plate may be formed from steel and may have an opening to allow it to freely slide along the rod. A clamping nut can be provided behind the clamping plate. The clamping nut may be, threadably attached to the rod such that rotation of the nut will cause the clamping plate to tightly clamp against the formwork panels. The nut or rod can be provided with means to prevent the nut from being totally removed from the rod such that the nut cannot inadvertently be lost. Of course, other forms of clamping nut equivalents can be used.